The present invention relates in general to a new magnetic tape cassette and more particularly to a magnetic tape cassette which houses tape reels in the cassette casing, the tape reel including a upper flange, and which is provided with a window on its upper surface in order to observe an inside magnetic tape.
As is well known, magnetic tape cassettes comprise a supply reel and a take-up reel onto which a magnetic tape is wound, a cassette casing which houses the reels and a tape cover member preventing the magnetic tape at the front of the cassette casing from dust and damage, the tape cover member being rotatably mounted at both ends of the front edge of the cassette casing by means of two pins.
The cassette casing comprises rectangular lower and upper shells and is formed by joining the upper and lower shells by means of screws or the like. The upper shell constituting the upper surface of the cassette casing is provided with a window. The window is provided with a transparent plate integral with the upper shell, so that the inside tape reels can be observed from the window through the transparent plate.
The tape reel comprises an axle and upper and lower flanges. The lower flange (reel hub) is made of a transparent resin, the peripheral surface of which has teeth.
The upper flange is made of a transparent material, so that the amount of the magnetic tape remaining on the tape reel can be seen from above. The reel is provided with an opening allowing a clamp piece, which clamps one end of the magnetic tape, ingress and egress.
Since the upper flange of the tape reel of the prior art magnetic tape cassette is made of a transparent resin so that the amount of magnetic tape remaining can be seen, the following problems have arisen.
First, since the upper flange is transparent, dust and/or marks on the surface of the flange are very conspicuous, whereupon the exterior appearance is unattractive. The flange can be designed so as to suppress dust and/or damage, but it is impossible to fully eliminate dust and/or marks. Because fine dust is often deposited on the inside surfaces of the metallic mold in which the flange is fabricated of resin by way of injection molding, the surface of finished flanges is often dusty. Furthermore, marks often appear on the inside surfaces of metallic molds. The inside surfaces of a metallic mold are corroded by gasses produced by the resin, which damage the inside surfaces generating scars. Furthermore, scars are often produced when the finished flanges are removed. The upper flanges can also be damaged due to collision with one another while in storage. The surface of flange may also be damaged while in a reel-converying tray after the tape reel is assembled but before the magnetic tape is wound thereon.
Furthermore, the surface of the upper flange may be damaged by a contact needle used to measure whether the flange wobbles as the tape reel rotates. Concretely, this kind of measurement can be performed optically or by contact. In the optical-type measurement, the target to be measured is illuminated and the reflected light is monitored in order to determine whether or not the flange oscillates. Therefore, a transparent upper flange requires contact-type measurement. Since the contact-type measurement is carried out by bringing a contact needle into contact with the surface of the measured object, the upper flange may be damaged by the contact needle.